1. Field
An aspect of the present invention relates to anode active materials, methods of preparing the same, anodes including the anode active materials, and lithium batteries including the anodes.
2. Description of the Related Art
Non-aqueous electrolytic secondary batteries including an anode containing a lithium-based compound are used in a wide range of applications due to their high voltage and high energy density. Electric vehicles, such as a hybrid electric vehicle (HEV) or a plug-in hybrid electric vehicle (PHEV), need to be charged with a large amount of electricity and discharge a large amount of electricity, and are used for a long period of time. Thus, they require a lithium battery having high capacity and excellent lifetime characteristics.
Metallic lithium has been often studied for use as an anode material due to its high battery capacity. However, metallic lithium is unstable and highly reactive, and thus, sensitive to heat or impacts, and thus, is explosive. An anode including metallic lithium may have a great amount of dendrite lithium at its surface during charging, and thus, may have a low charge/discharge efficiency or may be short-circuited with respect to a cathode.
An anode form of a carbonaceous material operates in a rocking-chair manner in which lithium ions existing in an electrolytic solution are intercalated into or deintercalated from between crystalline surfaces of the carbonaceous material, thereby performing oxidization/reduction reactions. A carbonaceous anode is porous, and thus, is resistant to volumetric expansion during charging or discharging, and thus, stable. However, the porous structure also attributes to a low battery capacity of the carbonaceous anode. For example, graphite having high crystallinity has a theoretical capacity of 372 mAh/g when used in LiC6. The theoretical capacity described above is about 10% of a theoretical capacity of metallic lithium, that is, 3860 mAh/g. In addition, since the flat voltage of the carbonaceous anode is about 0 V with respect to metallic lithium, metallic lithium may precipitate at the surface of the carbonaceous anode.
Meanwhile, molybdenum-based oxide anodes (MoO2 or the like) have a relatively low charge and discharge voltage (about 1.5 V vs. lithium (Li)), and high electrical capacity per unit volume and high electrical capacity per unit weight. However, molybdenum-based oxide electrodes undergo a large volume change during charging and discharging, and thus, lifetime characteristics thereof are deteriorated.